<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>天气案例_监视属性_简写</title>
  <script src="../js/vue.js"></script>
</head>

<body>
  <div id="root">
    <h2>今天天气很{{info}}</h2>
    <button @click="isHot = !isHot">切换天气</button>
  </div>

  <script>
    Vue.config.productionTip = false

    const vm = new Vue({
      el: '#root',
      data: {
        isHot: true
      },
      computed: {
        info() {
          return this.isHot ? '炎热' : '凉爽'
        }
      },
      watch: {
        /* isHot: {
          // 初始化时让handler调用一下
          // immediate: true,
          // deep: true, // 深度监视
          // handler什么时候调用？当isHot发生改变时
          handler(newValue, oldValue) {
            console.log("newValue:",newValue,",oldValue:", oldValue)
          }
        } */
        // // 简写
        // isHot(newValue, oldValue) {
        //   console.log("newValue:",newValue,",oldValue:", oldValue)
        // }
      }
    })

    vm.$watch('isHot', function (newValue, oldValue) {
      console.log("newValue:", newValue, ",oldValue:", oldValue)
    })
  </script>
</body>

</html>